Not the guy you’re responding to, but I also watched the movies before watching TOS. Well I actually did try watching TOS first, but “The Cage” turned me off to it for awhile. Anyway I honestly recommend this approach to anyone who is struggling to get into TOS. The movies stand on their own pretty much, even WoK gives you all the information you need to enjoy the movie. It’s a good way to get into the characters in a more accessible format.
I watched them all as a kid with my mom and we watched all the movies in theaters. Other than the movies I’ve never had the urge to go back and watch except for the very occasional nostalgia for a specific scene in an episode. I’ll always have love in my heart for TOS but it is very much a product of its time and I can’t blame anyone for struggling to get into it now. Best recommendation is to watch it with an old school trek fan because their reactions and excitement can amp up the experience a lot. Gotta be a fan that doesn’t take it too seriously because you also need the freedom to laugh at how silly some of it is when it’s not trying to be